Crock-resistant fabric



United States Patent 3,219,513 CRUCK-RESKSTANT FABREC John Wharton,Mobile, Ala., assignor to Courtaulds (North America) Inc., a corporationof Alabama No Drawing. Filed Dec. 6, 1061, Ser. No. 157,588 1 Claim.(Cl. 161-87) This invention relates to colored rayon staple fiber, andin particular to colored rayon staple fiber having high resistance tocrocking, both wet and dry, and to yarn and fabric made therefrom.

Rayon, i.e., regenerated cellulose, fiber is the least expensive of allsynthetic fibers. It is possessed of numerous attractive propertieswhich permit its employment in a wide range of applications. However,there remain some uses for which rayon is not as well suited as might bedesired. Thus, for example, the use of rayon in upholstery fabrics hasbeen somewhat limited because of its tendency to exhibit crocking,particularly when wet. Crocking is a term used to described the rubbingoff of dye or color from a fabric.

Thus, the tendency of colored rayon to crock is par ticularlyobjectionable in upholstery fabrics from which the color may rub offonto white or light colored clothing. It is also objectionable ingarment fabrics, e.g. in linings and in colored undergarments.

Resistance to crocking is rated according to a standard techniqueidentified as AATCC Test Procedure 8-1957. In general this measures thedegree to which color is transferred when the colored fabric in questionis rubbed against a piece of white cloth in a particular way. Manyfabric purchasers specify a minimum crock resistance and fabrics havingless than this cannot be sold. For automobile seat fabrics, for example,a minimum wet crock rating of three is specified and fabrics having lessthan this cannot be sold for automobile upholstery. Considering the sizeof the automobile market a wet crock rating of 3 is therefore in aneconomic sense, a critical rating.

Rayon fiber can, of course, be dyed after it is spun or after it is madeinto cloth. For many reasons, however, it is desirable to mix thecoloring agent with the viscose solution and form the fibers with thecolor already deposited within them. This technique is referred to inthe art as spin dyeing or solution dyeing. It is Widely practiced withazo dyestuffs, vat dyestuffs, carbon black, inorganic oxides and otherstable coloring materials. Generally fiber made in this way is superiorto fiber colored in other ways in its resistance to crocking; however,the crocking resistance of spun-dyed rayon textile fiber has still leftmuch to be desired.

In present day use there are three general types of rayon fiber. Thefirst, which may be referred to as normal textile fiber, ischaracterized in having a low degree of crystallinity, say 30 to 40% asdetermined by the X-ray method. It has an elongation of say 16 to 21%dry and 18 to 25% wet. The individual fibers have crenulated surfacesand a very pronounced skin-core structure. For most textile purposesthis fiber is used in the staple form.

Recently there has been introduced a relatively new type of rayon, alsospecifically for textile purposes. This material has a high degree ofcrystallinity, generally over 50%, and normally on the order of 65%. Ithas a generally circular cross-section and an even surface. It has anelongation of not more than say 10% dry and 12% wet. It, too, is usuallyemployed as staple fiber.

3,2l9,5l3 Patented Nov. 23, 1065 ice A third type of rayon currentlybeing made in large volume is the type usually employed in tire yarn. Itis characterized by a relatively low degree of crystallinity, i.e., lessthan say 45%, a high extensibility (say 22 to 35% dry and 28 to 45%wet), a smooth non-crenulated skin and substantially no skin-corestructure. Such rayon has not customarily been used for textilepurposes. It is made and used as continuous filament yarn rather thanstaple and it is of course not colored.

It has now been discovered that when filaments of a type somewhatsimilar to this third type are spun dyed, cut up into staple and thenconverted into fabric, the fabric so obtained has remarkably highresistance to wet crocking.

The invention thus comprises a rayon staple fiber having a degree ofcrystallinity below about 45% (as determined by X-ray methods), a dryextensibility of above about 20%, a wet extensibility of above about28%, a substantially all-skin structure and containing at least about 2%by weight coloring matter evenly distributed across its cross section.

The invention further comprises yarns and fabrics made from such staplefiber.

In manufacturing fiber of this type, viscose containing less than about8.5% cellulose, normally 6 to 7.5% cellulose, and more than say 5%NaOI-I, preferably 6 to 7.5% NaOH and having a '7 number of at least 35,usually between about 37 and about 65, is spun into an acid spinningbath. The bath contains not more than about 10% H 50 usually betweenabout 5.5 and about 8.5% H 80 not less than about 3.0% ZnSO usuallybetween about 3 and about 7% ZnSO, and between about 12 and about 23% NaSO The proportion of Na SO will in general depend on the zinc content,i.e., 3% ZnSO will call for about 23% Na SO and 7% ZnSo, will requireabout 12% Na SO The temperature of the bath will be above about 45 C.,usually between about 55 C. and about C. As noted above the viscose willalso contain at least 2% coloring material based on cellulose. Theprecise amount will of course depend on the material and on the shadedesired, but usually it will be between about 2.5 and about 4.5% on theweight of cellulose.

The spinning is further conducted in the presence of a viscose modifier.The modifier is preferably added to the viscose, where it is normallypresent in a proportion between about 0.008 and about 4.0%, on theweight of viscose and preferably between about 0.03 and about 1% on theweight of viscose. In certain cases, the modifier may be added to thespinning bath where it will usually constitute between about 0.1 andabout 1.0% by weight of the bath.

The use of viscose modifiers has been known in the rayon industry forseveral years. These substances vary greatly in chemical composition andappear to differ among one another in the mechanism through which theyoperate. However, the effect in every case is to produce filaments whichhave thick skins or are all skin. The filaments may be oval, round orbean-shaped in cross section and have a smooth skin, free from thecrcnulations normally found in textile grade rayon,

Among the substances which have been found useful as modifiers arequaternary ammonium compounds as disclosed in United States Patent2,536,014, aliphatic monoamines as disclosed in United States Patent2,535,044, aliphatic diamines as disclosed in British Patent 762,772,salts of N-substituted dithiocarbamic acids, ethers of the formula RO(CHCH O),,R where R is alkyl or aryl, n

is an integer from 1 to 4 and R is hydrogen, alkyl, or aryl, asdisclosed in British Patent 741,728 and polyethylene glycols of formulaHO(CH CH O), H where n is at least 4, as disclosed in United StatesPatent 2,696,423. Generally it is preferred to use polyethylene glycolmodifiers having a molecular weight from about 1500 to about 10,000.

Preferably the pigment or coloring matter is introduced into the viscoseby means of a non-aging viscose-compatible carrier, such, for example,as sodium carboxymethyl cellulose or the salts of polyacrylic orpolymeth' acrylic acid as disclosed in United States Patents 2,783,- 8and 2,993,018. Alternatively, in accordance with another conventionaltechnique, a portion of the viscose can be withdrawn from the mainstream just before extrusion, mixed with the coloring matter andreunited with the main stream. It is, of course, also possible to mixthe color with batches of viscose in spinning concentrations initially.Difliculties are experienced here, however, in maintaining constantshades.

After spinning, the viscose filaments may be withdrawn from the spinningbath, stretched between about 40 and about 100% either in air or in adilute (say 1 to 4% H 80 acid bath at say 60 to 100 C., and cut up intostaple. The staple may then be washed in accordance with conventionalpractice, and dried.

Alternatively the filaments after stretching may be washed and dried inthe form of tow and subsequently cut into staple after they have beendried.

Colored staple fiber made as indicated will have a thick skin or beall-skin; have a smooth non-crenulated surface and a circular, oval orbean-shaped cross-section, It will have a crystallinity of less than45%, usually between about 35 to about 40%, as determined 'by X-raytechniques, an extensibility (wet) of more than 28% (usually from 30 toabout 45%) and an extensibility (dry) of more than (usually from 20 to35%). It will have the coloring material distributed uniformlythroughout its cross-section. It is of interest that fibers made in thisway show little or no fibrillation when agitated at high velocity inpure water.

Staple fiber having the characteristics described can be made into yarnsby any convenient technique, using the cotton system, for example, andthen woven or knitted into fabrics. They may also be used to make theso-called non woven fabrics. Such fabrics are of excellent hand andappearance and have in general a crock rating at least greater thancomparable fabrics made out of conventional textile grade rayon. Theywill have in general a wet crock rating above 3 and in many instancesabove 4. As such they are of particular utility in upholstery andgarment fabrics.

It will be understood that viscose rayon fibers made in accordance withthe invention may be used by themselves or blended with other types offibers, to make combination yarns or non-woven fabrics. Similarly yarnsmade wholly from the novel staple fiber may be used alone in themanufacture of woven or knitted fabrics, or in combination with yarnsmade of other fibers. The benefits of the invention become increasinglyimportant as the proportion of the novel rayon fibers in the yarn orfabric increases, However, they begin to have a noticeable effect whenthe proportion of the new fibers reaches about 25% by weight of theblend.

Among the fibers which may be blended with the novel staple fiber arefibers of cellulose esters, for example, cellulose acetate (acetonesoluble cellulose acetate or cellulose triacetate), and fibers ofsynthetic linear polymers, for example, of polyamides such as nylon 6 ornylon 66, of polyesters, for example, polyethylene terephthalate, ofpolyolefins such as polyethylene or polypropylene and of additionpolymers derived from acrylonitrile.

The invention will be further described with reference to the followingexamples which are given for purposes 4;. of illustration only and arenot to be taken as in any way limiting the scope of the claims.

Example 1 Spun dyed staple fiber A was produced by premixing 10 parts byweight of phthalocyanine blue containing 15% of an anionic dispersingagent (a sodium salt of a naphthalene sulfonic acid) into 90 parts of aviscose containing 7.5% cellulose and 6% sodium hydroxide and having agamma number of 60. After mixing and deaeration the pigmented viscosewas injected at constant rate through pumps into a cylindrical enclosedhigh speed mixer together with a larger quantity of filterednon-pigmented viscose of similar composition but containing 4% of apolyethylene glycol having a molecular weight of about 2000. Theproportions of pigmented and non-pigmented viscose were such as to givea final blend containing 3% phthalocyanine blue on cellulose. Thismixture was then deaerated and spun through 5000 hole 3 mil jets into aspinning bath containing 7.0% H 18.0% sodium sulfate and 5.0% ZnSO andhaving a temperature of 55 C. After a 70% stretch, fixation, cutting,washing and drying the 1 /2 denier pigmented staple fiber had tenacitiesof 3.8 g./den. dry and 2.5 g./-den. wet, and extensibilities of 24% dryand 34% wet. It had a smooth surface and a bean-shaped cross-section.Skin-core differentiation was not present. It had a crystallinity ofabout 38% and did not fibrillate after 2 hours beating in water at 400strokes/ min.

The fiber was made into a 30s count yarn which in turn was used to makea knitted stocking fabric,

A similar fabric was made from spun dyed conventional textile graderayon fiber (Fiber B) 1 /2 denier having a dry elongation of 17%, a wetelongation of 21%, a crystallinity of about 43% and containing 3%phthalocyanine blue. The two fabrics were then tested for crock rating.The results are shown below:

Example 2 To a viscose containing 6.5% cellulose and 5.5% NaOH andhaving a gamma number of 65 was added 3.5% on cellulose of a finelydispersed carbon black having an average ultimate particle size of 400-A. together with 15% on the weight of carbon black of a nonionicdispersing agent and 0.5% on the weight of viscose of a mixedcoagulation modifier containing principally polyethylene glycol and anethylene oxide lauryl amine condensation product. The viscose was spuninto a bath con taining 6.5% H 80 14% Na SO and 6.5% ZnSO at 60 C. Thetow was stretched 83%, fixed in an acid bath at C. and cut into staple.

The black staple had tenacities of 4.1 g./den. dry, and 3.0 g./den. wet.Its extensibilities were 22% dry and 36% wet. It had a homogeneous,oval, non-crenulated cross-section and a crystallinity of about 40%. Itdid not fibrillate under the conditions described in Example 1.

The staple fiber was spun into 20s yarn and then woven into a plainweave cloth. The cloth showed a wet crocking index of 4.0.

A similar fabric made from the same denier conventional textile gradeyarn having a wet extension of 20%, a dry extensibility of 17% and acrystallinity of 42% showed a wet crock rating below 3.

I claim:

A colored fabric characterized by its high resistance to wet crockingand composed of at least 25 by weight of viscose staple fiber having acrystallinity below about 40%, a dry extensibility of greater than 20%and a wet extensibility of greater than 28%, having a substantiallyleast 3.

References Cited by the Examiner UNITED STATES PATENTS Helm et a1106-164 Lutgerhorst 1854 Wegrnann et a1 106165 Thurnm 106165 Howsmon106-165 Vosters 106165 Cox et a1 2882 Matray et al 2882 Mix 106168DONALD W. PARKER, Primary Examiner. Schlack 1 10 MERVIN STEIN, Examiner.

